Cortisol and corticosterone productions of isolated adrenal cells in neonatal rabbits.

Isolated adrenal cells of rabbits aged from 0 h to day 40 after birth were incubated for 2 h in the presence of ACTH. Thin-layer chromatography and the fluorimetric method were used to evaluate the products of these adrenal cells separately for cortisol and corticosterone. Cortisol production by adrenal cells in response to ACTH (0.1 mU) was found to be highest between 0 and 8 h after birth (0.522 +/- 0.049 mug/105 cells; mean +/- SEM). A decrease was observed at 9-20 h and this was further followed by a steady decrease up to day 35-40. Corticosterone production was 0.206 +/- 0.042 mug/105 cells between 0 and 8 h after birth. Subsequently, this level was evenly maintained up to 12-14, but it tended to increase on day 35-40. The level of cortisol production was significantly higher than that of corticosterone production at 0-20 h after birth, while the former was significantly lower than the latter from day 12-14 onwards. The ratio of corticosterone to total corticosteroids (cortisol + corticosterone) was very low (0.28 +/- 0.04) at 0-8 h after birth, but showed a progressive rise up to day 35-40, when it was 0.95 +/- 0.01. The results of the present study show that cortisol is the pre-dominant product of the adrenal cells in rabbits during early post-natal life.